If you consider your characters to have their own personalities, interests, motivations, and other such characteristics that would make them more than just a collection of pixels used to win the game, then I'd called that role playing. Anything beyond that is just varying degrees of RP decadence.
personaly, i'd have to agree with that. IMO roleplaying doesn't require interaction with other people, it only requires that when player is playing a character they are not thinking in terms of "what would I do in this situation" but rather "what would this particular character that i'm playing right now - would do in this situation"
that is not to dismiss that sometimes we base our characters on ourselves and IMO that is totally fine, but as long as they are still their own distinct characters that just happen to share their set of morals with a player - it still counts.
P.S. becasue thoughts occur to me in batches - roleplaying is essentially not unlike writing in real time, sometimes colaboratively, sometimes - on your own. its creative expression.